1. Field of the Invention
The present invention relates to a cooling apparatus and, more particularly, to a cooling apparatus, for a liquid cooled internal combustion engine, such as a cooling apparatus for an automobile engine.
2. Description of the Related Art
Coolant for a liquid-cooled internal combustion engine is conventionally circulated by a pump that is driven by the engine. When the engine is started, the idling engine speed is increased both to warm-up the engine and to prevent the engine from stalling. For a coolant pump driven by the engine, the average flow rate of coolant increases because the speed of rotation of the pump increases as the engine picks up speed. Since heat transfer to the coolant increases as the average flow rate of the coolant increases, it is difficult to warm up the engine immediately after the engine is started.
To solve this problem, Japanese Kokai No. 8-14043 discloses a coolant pump driven by an electrical motor that is stopped when the engine is being warmed up.
However, stopping the coolant pump decreases the heat transfer to the coolant so that the coolant in the engine often boils locally. Local boiling of the coolant may cause the engine (cylinder head, cylinder block, etc.) to deform, thus damaging the engine.
An object of the present invention is to eliminate the drawbacks mentioned above by preventing damage to an engine (internal combustion engine) and promoting the warming-up of the engine.
To achieve the object, according to an aspect of the present invention, there is provided a cooling apparatus for a liquid-cooled internal combustion engine (10), comprising: a radiator (20) that cools coolant discharged from the engine bypasses the radiator (20) and returns to the engine (10); and a heat exchanger (90) that exchanges heat between coolant discharged from the engine (10) and a working oil; wherein when the temperature of the coolant discharged from the engine (10) is below a predetermined temperature, the flow rate of the coolant returned to the engine (10) is restricted to between 1 and 5 L/min, and the coolant discharged from the engine (10) is allowed to flow through the radiator (20) and the bypass passage (30) but not the heat exchanger (90); and when the temperature of the coolant discharged from the engine is above the predetermined temperature, the coolant discharged from the engine is allowed to flow through the radiator (20), the bypass passage (30), and the heater exchanger (90).
With this arrangement, when the temperature of the coolant is below a predetermined temperature, the coolant is circulated at small flow rate of 1 to 5 L/min between the bypass passage (30) and the liquid-cooled internal combustion engine (10) and, hence, it is possible to prevent the coolant in the liquid-cooled internal combustion engine (10) from boiling locally.
Moreover, it is possible to shorten the time necessary to complete the warming-up, in comparison with the circulation of the coolant at flow rate of 5 L/min or more. Consequently, the warming-up can be promoted while preventing the liquid-cooled internal combustion engine (cylinder head or cylinder block, etc.) from being deformed locally due to heat.
When the temperature of the coolant is below a predetermined temperature, the coolant is circulated at least between the liquid-cooled internal combustion engine (10) and the bypass passage (30) without passing in the oil heat exchanger (90) and, hence, it is possible to prevent the heat of the liquid-cooled internal combustion engine (10) from being absorbed by the working oil through the coolant. Therefore, the warming-up can be further promoted.
The oil heater exchanger (90) exchanges heat between working oil in a torque converter (80) for an automatic transmission and the coolant.
According to another aspect of the present invention, a cooling apparatus for a liquid-cooled internal combustion engine (10); comprising: a radiator (20) that cools coolant discharged from the engine (10) and returns the cooled coolant to the engine (10); a bypass passage (30) through which the coolant discharged from the engine (10) bypasses the radiator (20) and returns to the engine (10); and a heater exchanger (60) that exchange heat between coolant discharged from the engine (10) and ambient air; wherein before the engine is warmed-up of the engine, the flow rate of the coolant returned to the engine is restricted to between 1 and 5 L/min, and the coolant discharged from the engine (10) is allowed to flow through the radiator (20), the bypass passage (30) but not heat exchanger (60); and after the engine is warmed up, the coolant discharged by the engine is allowed to flow through the radiator (20), the bypass passage (30) and the heater exchanger (60).
With this arrangement, when the temperature of the coolant is below a predetermined temperature, the coolant is circulated at small flow rate of 1 to 5 L/min between the bypass passage (30) and the liquid-cooled internal combustion engine (10) and, hence, it is possible to prevent the coolant in the liquid-cooled internal combustion engine (10) from boiling locally.
Moreover, it is possible to shorten the time necessary to complete the warming-up, in comparison with the circulation of the coolant at flow rate of 5 L/min or more. Consequently, the warming-up can be promoted while preventing the liquid-cooled internal combustion engine (cylinder head or cylinder block, etc.) from being deformed locally due to heat.
Since when the temperature of the coolant is below a predetermined temperature, the coolant is circulated at least between the liquid-cooled internal combustion engine (10) and the bypass passage (30) without passing in the heating heat exchanger (60), it is possible to prevent the heat of the liquid-cooled internal combustion engine (10) from being absorbed by the air through the coolant. Therefore, the warming-up can be further promoted.
In addition to the foregoing, when the temperature of the coolant is above a predetermined temperature, the coolant is circulated to the heating heat exchanger (60) and, hence, the warming-up can be quickly carried out by the coolant of high temperature when the ambient temperature is low.
According to still another aspect of the present invention, there is provided a cooling apparatus for a liquid-cooled internal combustion engine (10); comprising: a radiator (20) that cools coolant discharged from the engine (10) and returns the cooled coolant to the engine (10); a bypass passage (30) through which the coolant discharged from the engine (10) bypasses the radiator (20) and returns to the engine (10); and a heater exchanger (90) that exchange heat between coolant discharged from the engine (10) and a working oil; wherein when the temperature of coolant discharged from the engine is below a predetermined temperature, the flow rate of the coolant returned to the engine is restricted between 1 and 5 L/min, and the coolant discharged from the engine (10) is allowed to flow through only the radiator (20) and the bypass passage (30) but not the heater exchanger (90); when the temperature of the coolant is above the predetermined temperature, the coolant discharged from the engine is allowed to flow through the radiator (20), the bypass passage (30), and the oil heat exchanger (90); when the engine (10) is warmed up, the cooling liquid is circulated to the radiator (20) so that the temperature of the coolant is approximately in the range of 95xc2x0 C. to 110xc2x0 C.
With this structure, when the temperature of the coolant is below a predetermined temperature, the coolant is circulated at small flow rate of 1 to 5 L/min between the bypass passage (30) and the liquid-cooled internal combustion engine (10) and, hence, it is possible to prevent the coolant in the liquid-cooled internal combustion engine (10) from boiling locally. Moreover, it is possible to shorten the time necessary to complete the warming-up, in comparison with the circulation of the coolant at flow rate of 5 L/min or more. Consequently, the warming-up can be promoted while preventing the liquid-cooled internal combustion engine (cylinder head or cylinder block, etc.) from being deformed locally due to heat.
When the temperature of the coolant is below a predetermined temperature, the coolant is circulated at least between the liquid-cooled internal combustion engine (10) and the bypass passage (30) without passing in the oil heat exchanger (90) and, hence, it is possible to prevent the heat of the liquid-cooled internal combustion engine (10) from being absorbed by the working oil through the coolant. Consequently, the warming-up can be further promoted.
When the temperature of the coolant is above a predetermined value, the coolant is circulated to the oil exchanger (90) and, hence, when the temperature of the working oil is low, the working oil can be heated by the coolant of high temperature.
Consequently, not only can the warming-up can be promoted, but also the fuel consumption can be improved by increasing the temperature of the working oil to thereby reduce the friction loss thereof.
Since the control is made so that the temperature of the coolant is maintained in the range of 95xc2x0 C. to 110xc2x0 C. when the warming-up is completed, the fuel consumption can be further improved by increasing the temperature of the lubricant (engine oil) which is circulated in the liquid-cooled internal combustion engine (10) to thereby reduce the friction loss.
Note that the reference numerals of the components (means) recited above exemplarily correspond to those in embodiments of the invention which will be discussed below.